Synthesis and biological evaluation of 2-phenyl-4-aminoquinolines as potential antifungal agents

A series of 2-phenyl-4-aminoquinolines were designed, synthesized and evaluated for their antifungal activities against three phytopathogenic fungi in vitro. All of the target compounds were fully elucidated by ¹H NMR, ¹³C NMR and HRMS spectra. The results indicated that most of the target compounds demonstrated significant activities against the tested fungi. Among them, compound 6e exhibited more promising inhibitory activities against C. lunata (EC₅₀ = 13.3 μg/mL), P. grisea (EC₅₀ = 14.4 μg/mL) and A. alternate (EC₅₀ = 15.6 μg/mL), superior to azoxystrobin, a commercial agricultural fungicide. The structure-activity relationship (SAR) revealed that the aniline moiety at position 4 of the quinoline scaffold played a key role in the potency of a compound. And the substitution positions of the aniline moiety significantly influenced the activities. These encouraging results yielded a variety of 2-phenylquinolines bearing an aniline moiety acting as promising antifungal agents.